Some of you know that I love to chase down the sources of horticultural beliefs. If you have ever spent time on any plant forum you know the common advice is to keep your plants root bound, or at least when you repot give the roots only an "extra fingers width" on each side the pot. My question is where does that advice originate? Why do we believe it? Is this really good growing advice or just an old wives tale? Are plants in the rain forest root bound? I understand that nursery men prefer to start their plants in small pots and allow the roots to fill it before stepping the seedling up to a larger pot. My understanding is they do this in order to encourage a hearty root system first. But it appears some growers may have taken this advice to excess and always keep their plant's root bound. Should we always keep our plants in pots so small their roots are for ever crowded, or give them space to grow? We always have new growers looking for good growing advice. If you have adopted a small pot policy please tell us why. If you are an experienced grower and prefer a tight pot method I would enjoy knowing the reasoning. Many of you don't know that I have written for years for a variety of magazines and I have another train of thought in this area. I am now working on a new article to explain about plant growth, a plant's need for oxygen around its roots as well as how to keep their root systems healthy. This discussion will help me to formulate my article. I am here primarily to listen, not to offer my observations. If I find useful quotes I would like to be able to use them in the article. If you are new to growing, please chime in. This post is now on 5 forums and I plan to combine the best responses into the final piece followed by scientific observations from botanists and professional growers. Steve
Here's one opinion: http://chestofbooks.com/gardening-horticulture/Gardener-3/Small-Pots-In-Forcing.html Paragraph 4 expresses the gist of the author's theory.
Can you verify the link? I can't find any paragraphs, just other links but I would like to read it. Steve
The only thing that comes to mind for me would be time and expense for growers. If we put 4 inch tall seedling in a 40 gallon pot, the entire pot of soil must be kept moist. But it would take less time and water to keep a one gallon or 4 inch pot moist. But it may depend on the pot and the plant. In big pots with tiny plants, its mostly the surface that seems to dry. But if we look at many plants in their natural habitats, they germinate and grow in virtually unlimited rootball spaces. Just after I posted this, before an edit, I remembered needed to run out and water little trees in one gallon pots. Those pots don't hold much soil, and the trees are growing. So the pots dry slightly quicker now. I'm planning to put the 3 together in thirds of a big 20 gallon pot with wood dividers between their roots.
Steve, you have to scroll down the page to get to the article. I generally assumed that the reason for going up in size gradually was to control growth, limit the need for water and fertilizer (and to keep from wasting them). I also have the idea, I don't know from where, that it helps prevent diseases from taking hold in the excess soil that the plant's roots have not grown into. Probably the main reason is just one of space. If you have all your seedlings in 10 gallon pots, you won't be able to fit very many of them on the grow bench or under the grow light or whatever. There definitely seems to be error on the other side of this issue in the trade. I mean that many nursery plants are sold so root bound that the root system is damaged.
Link works OK for me. Here's my theory: growers use small pots for obvious reasons. More individual plants equal more money to be made. Folks buy these plants, observe their rootbound condition---and figure that this is the way the plants should be grown. When the time comes to repot, the plant-owners' thought is 'Well, I'd better keep it in a small pot, like it was when I got it.' The assumption is made that the grower's motive was the good of the plant---not profit. A lovely fiction, but fiction nonetheless! So, I think that this idea is what might be termed an 'urban legend' sorta thing...it began with a fact (plants sold in small pots), has been perpetuated by hearsay and habit, and is now so firmly imbedded in the general consciousness that not even dynamite could dislodge it. All the more reason that this forum and Steve's outstanding site are so vitally important: people need to know the truth.
Great responses, and I'm sure all are correct. My interest is in why a home grower often answers on sites like this that plants should never be stepped up quickly and often use some your same of the same reasoning to explain why. Do plants really like to be root bound? Obviously some plants will bloom faster if stressed by restricting the growth of the roots but is that always good advice. Some plants in nature grow in and among rocks so their roots would naturally be restricted to some degree. Hoya appear to bloom faster both in the ground and in pots if restricted. But at the same time if the roots are highly restricted the plants are suffering from stress as a result. I have a large Anthurium veitchii which is normally an epiphytic plant that grows in the wet rain forest of Colombia. The plant was growing marvelously and then suddenly dropped every leaf, some of which were over four feet long, in a few weeks. I immediately went to repot it and found the roots were highly restricted and the plant was apparently under stress. If my theory is correct the plant threw the leaves in order to restrict its own grown as a survival instinct. So immediately we took it out of the pot and repotted it so it can now grow as an epiphyte with no restriction on the roots at all as it grows naturally in the rain forest. The roots hang three feet beneath the orchid basket now and new leaves are beginning to form. I am just trying to learn why "root bound" is a commonly stressed "theory" among home growers. I'm sure it makes some plants perform better in terms of blooms but in the end is the plant as happy as the grower? The grower is pleased because of the blooms but when a plant suddenly gives up its life there must be a cause. Most of us tend to blame that on excess water in the pot but is that factual? Sometimes I see evidence that would dispute that fact since my Anthurium had huge roots, little room for them to expand and almost no soil left in the pot. I highly doubt it died of too much water since it lives normally in a very wet rain forest. My mind can be changed but I need to hear some good reasoning to persuade me. In my personal rain forest we grow many plants in no pots at all and they flourish and bloom and is suspect that is because they experience almost no stress. If I am wrong, please convince me but also explain why. I need to hear both sides in order to write a well balanced article. The second photo was the Anthurium veitchii in happier times. The orchid basket is 12 inches square. Steve
I can't say I would advocate growing a potted plant until it is rootbound, but there are definite issues with growing small plants in pots that are too large, and that is why I prefer to gradually increase the container size over the years. The main issue with a very large container compared to the size of the plant is that the potting medium can stay too wet and this leads to a lack of oxygen around the plant roots. The potting mix does not dry out fast enough because the plant is not transpiring much water relative to the amount in the container, but it is not too much water that is the main problem, rather a lack of aeration in the root zone. Obviously epiphytes grown in baskets don't suffer the same problem. Here are links to a couple of articles that explain it much better and go into the related issues with far more detail than I could: Overpotting Why the Earth Is Not Like a Pot Another one from the same source: Intact Rootball Vs. Rootbound The articles are specifically about bonsai trees but the same issues will apply to any terrestial plants grown in pots.
I agree. But that still leaves my question of why so many growers only want to step up a root bound plant to a one inch larger pot? Wouldn't the addition of a better soil that drains quickly, does not provide wet areas for saprophytes to develop and is more suitable to the needs of the plant and also allows proper drainage do the same thing while satisfying th plant;s needs? At least the plants that live in a rain forest don't normally grow in Miracle Grow but a much looser mix. Shouldn't we take that into consideration? I recently did a fair sized study on rain forest soils and they aren't even close to the stuff we buy at Home Depot. Tight roots cause stress which do in fact in some cases case plants to flower. However in nature many plants flower at the beginning of the rainy season once they have been stressed due to lack of water for months. Others bloom at the end of the rainy season, likely as a DNA response that tells the plant it must reproduce now to preserve the species. I am still trying to understand why so many growers freely offer advice to do things that may not actually benefit the plant. I have received over 50 personal email today on this subject and the majority tend to believe growers prefer to force a plant to live as they want it to live rather than treating the plant as it needs to live. Just last week I read a response from a lady that had just purchased a notoriously difficult Asian species that is difficult to bloom. She said she would "force it into submission and make it bloom". I'm not sure the plant will bend to her "demands". Could that be why so many house plants end up in the trash every year? Stress can be a good thing but it can also be very bad. In the case of my Anthurium veitchii above my observation is the soil was exhausted and the plant had hung on as long as possible without enough nutrition. My fault since I had not checked the roots often enough. There is so much still to consider but at least I am now rounding up tons of notes and email from good growers offering their reasoning. Once I can compare that to the information from several scientists just maybe I'll be able to compose a descent article that can explain much of this to any grower willing to read it and make a better informed decision. I'm still looking for more info so please keep it coming. I would really like to hear from anyone that believes that "root bound" is the only way to grow. I promise, I won't chastise anyone's answers. I simply want to understand the reasoning. Thanks! Steve
I'm not a commercial grower, just have houseplant and balcony plants. I was told the same story that maf related - that in too large a pot, the soil would stay too wet with no roots to take up the moisture. So then I go and demonstrate what I was told - the four plants I potted up into nice large pots in the last two years have died, and all my root bound plants are doing fine. So I don't repot them because I'm scared, and also because I'm lazy. If the plants would look worse, I'd probably repot them. Maybe growers are on to us clueless plant purchasers. I think we're known to kill more plants from overwatering than from anything else. From my personal experience, keeping the plants rootbound doesn't outright kill them. People who have a dead plant tend to go back to the supplier with a complaint. In your last post, you asked about the advice growers give. Why they'd sell plants in small pots is a different issue. If the plant is too heavy for us to carry, they have to deliver it or we can't buy it.
Thanks for the response again. I fully understand about the soil. One of the things I have tried to explain on the aroid forum when it was in use is soils need to be modified based on the type of plant. Commercial growers often do not do that since it is less expensive and less time consuming. That is understandable. Home growers almost never do it and simply use soil out of the bag and many just say it is easier to water less even if the plant wants something else. In our atrium we grow all of our plants as closely as possible to the way they grow in nature. When we began quite a few years ago we did the same thing inside the house and modified all our soil so it would not accommodate saprophytic bacteria which is the cause of root rot. To do that for tropical species requires they be mixed to prevent the soil from staying perpetually wet, only damp and evenly moist. We have hundreds of species in the atrium and many are in pots........hundreds of pots. Even though we water with an overhead misting system 5 days a week in summer up to 10 minutes per day we rarely see root rot. The only difference is the way the soil is mixed. Roots actually grow faster in custom mixed soil and a very well established root system is important to foliar growth. We repot on a regular basis in order to make sure the roots are healthy as well as ensure the pots are not root bound. So far I've received over 50 responses to my query via private email as well as posts on other forums. Right now it appears many growers have yet to fully understand the importance of the soil and how its quality relates to the excess water retention, thus sickly root systems. Fear of repotting actually appears to be a major motivating factor in allowing plants to become root bound but I am still looking for more of the underlying causes of why growers believe leaving plants root bound is healthy for the plant since they rarely live that way in Nature. Why do you suppose many growers would rather not bother with mixing their own soil in order to help the plant grow in a more natural environment, even in a home? In order to make my article useful to home growers I need to be able to address the whys and hows as well as the causes and cures. Much of the time when I try to explain some of this in my posts on some forums all the explanations are soundly rejected by some. I think that is what I'm now trying to figure out. Do some of us simply rationalize the methods we prefer to fit our needs rather than those of the plants we love? Thanks again for the help. Steve
Of course we do. Human nature, #1. Human Nature,#2: Do what's easy, i.e. use soil from a bag. Human Nature, #3: Cling to beliefs because they are familiar, therefore reassuring. For many folks it is unsettling and uncomfortable to critically analyze something done for years---and then admit 'Hey, I was wrong!' Change is stressful. Evidence, no matter how cogent, which contradicts long-held beliefs is perceived as threatening and scary. To Be Denied! You Can Lead Folks To The Truth, But You Can't Make Them Think.
My grandmother always told me to keep many of my indoor plants rootbound to make them bloom. I never asked why, but they bloomed. Who knew? Hito
